Prediction of flow boiling heat transfer coefficient for carbon dioxide in minichannels and conventional channels

Abstract

In the paper presented are the results of calculations using authors own model to predict heat transfer coefficient during flow boiling of carbon dioxide. The experimental data from various researches were collected. Calculations were conducted for a full range of quality variation and a wide range of mass velocity. The aim of the study was to test the sensitivity of the in-house model. The results show the importance of taking into account the surface tension as the parameter exhibiting its importance in case of the flow in minichannels as well as the influence of reduced pressure. The calculations were accomplished to test the sensitivity of the heat transfer model with respect to selection of the appropriate two-phase flow multiplier, which is one of the elements of the heat transfer model. For that purpose correlations due to Müller-Steinhagen and Heck as well as the one due to Friedel were considered. Obtained results show a good consistency with experimental results, however the selection of two-phase flow multiplier does not significantly influence the consistency of calculations.Keywords: Heat transfer coefficient; Flow boiling; Carbon dioxide; Minichannels Nomenclature B-blowing parameter Bo -boiling number, q/GhLG

Comparison of predictive methods for flow boiling heat transfer in conventional channels and minichannels – the effect of reduced pressure

“…Figures 1 to 4 show the results of calculations of heat transfer coefficient for all data bank obtained using the described earlier flow boiling model described by Eq. (1), (2) and (6), supplemented by different definitions of the two-phase flow multiplier (3), (4) and (5). 7, where the reduced pressure is raised to power a.…”

“…Equation 1also includes the empirical correction P defined by equation (2). Occurring in the equation 1the two-phase multiplier is raised to the power n (n=0.76 for turbulent flow, n=2 for laminar flow).…”

An improved method for flow boiling heat transfer with account of the reduced pressure effect

“…Design of evaporators for use of the CO 2 requires the exact determination of heat transfer coefficient during flow boiling. Available in the literature empirical correlations give different results as compared to the results obtained experimentally [4,5]. There is hardly any robust and recommended correlation for the purpose of calculation of CO 2 two-phase heat transfer and _____________ * Corresponding author, e-mail: Blanka.Jakubowska@pg.edu.pl S1262 THERMAL SCIENCE: Year 2019, Vol.…”

Investigations on mixture preparation for two phase adiabatic pressure drop of R134a flowing in 5 mm diameter channel

“…is frequently encountered in industry and has been studied intensively for many years. The reliable prediction of flow parameters in two-phase flows is thereby an important aim; yet, heat transfer coefficients and pressure gradients predicted using leading methods often differ by more than 50% according to various reports [12][13][14].…”